1. Field of the Invention
The present invention relates to an apparatus for controlling the charging of a battery, e.g., a 240 V battery, on an electric vehicle which can be propelled to travel on roads by a propulsive motor energized by the battery.
2. Description of the Related Art
There has recently been proposed an electric vehicle which can be propelled to travel on roads by a propulsive motor energizable by a motor inverter to which electric energy is supplied from a battery, e.g., a 240 V battery, on the electric vehicle.
An air-conditioner mounted on the electric vehicle has a motor-driven compressor which can be actuated by an electric motor, referred to as an air-conditioner motor, energizable by an inverter. The inverter has input terminals connected to the battery on the electric vehicle. The air-conditioner with the motor-driven compressor will also be referred to as a motor-driven air conditioner.
On the electric vehicle, both the propulsive motor and the air-conditioner motor are energized by the charged electric energy from the battery. Because the mileage of the electric vehicle, which is based on the capacity of the battery, is shorter than the mileage of an ordinary automobile propelled by an internal combustion engine, which is based on the capacity of the fuel tank, it has been proposed to operate the air-conditioner on the electric vehicle in a pre-air-conditioning mode.
As disclosed in Japanese laid-open patent publication No. 5-147420, the pre-air-conditioning mode is a mode of operation carried out when the propulsive motor is de-energized, e.g., when the electric vehicle is stopped or parked. In the pre-air-conditioning mode, the battery on the electric vehicle is charged by an external power supply through a charger, and the air-conditioner is actuated through the charger while the battery is being charged, so that comfortable levels of temperature and humidity will be achieved in the passenger's compartment or cabin at a boarding time when the driver gets into the electric vehicle.
If the air-conditioner on the electric vehicle is continuously actuated while the electric vehicle is running, the mileage of the electric vehicle is reduced by about 20% because of the burden imposed on the battery by the air-conditioner. In the pre-air-conditioning mode, since the air-conditioner is actuated by electric energy supplied from the external power supply while the battery is being charged, the capacity of the battery is not reduced, and the cabin can be cooled down or heated up before the driver enters the cabin. Therefore, the pre-air-conditioning mode is an effective and useful feature on the electric vehicle.
AC power supplies available at home and business facilities normally are in the form of AC outlets at ratings of 200 V (200 V.about.240 V).multidot.30 A or 100 V (100 V.about.117 V).multidot.15 A. For charging the battery on the electric vehicle in a relatively short period of time, such as one or two hours, while the electric vehicle is parked, it is simple to connect the charger to an AC outlet at ratings of 200 V (200 V.about.240 V).multidot.15 A which is in most widespread use. Because the mileage of the electric vehicle, which is based on the capacity of the battery, is relatively short, it is an effective practice to charge the battery in one or two hours each time the electric vehicle is parked, for extending the mileage.
If the air-conditioner can be operated in the pre-air-conditioning mode while the electric vehicle is parked for such a short period of time, then the cabin can be air-conditioned to a comfortable environment before a boarding time.
The air-conditioner installed on an ordinary 4-wheeled electric vehicle normally has a power consumption rating of about 1.5 kVA, and the charger on the electric vehicle produces an output current of about 15 A. Therefore, when the battery on the electric vehicle is charged, the air-conditioner cannot be operated, and when the air-conditioner is operated, the battery on the electric vehicle cannot be charged.